1. Field of the Invention
The present invention relates generally to a method and apparatus for scheduling a Coordinated Multi-Point Transmission/Reception-enabled User Equipment (CoMP-enabled UE), and more particularly, to a resource allocation method and apparatus for facilitating efficient time and frequency resource management in a system supporting CoMP.
2. Description of the Related Art
Mobile communication systems have evolved into high-speed, high-quality wireless packet data communication systems that provide data and multimedia services beyond the early voice-oriented services. Recently, various mobile communication standards, such as, for example, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), and LTE-Advanced (LTE-A) defined in 3rd Generation Partnership Project (3GPP), High Rate Packet Data (HRPD) defined in 3rd Generation Partnership Project-2 (3GPP2), and 802.16 defined in Institute of Electrical and Electronics Engineers (IEEE), have been developed to support high-speed, high-quality wireless packet data communication services. Particularly, LTE is capable of facilitating high speed packet data transmission and maximizing throughput of a radio communication system with various radio access technologies. LTE-A is an evolved version of LTE that improves data transmission capability.
The existing 3rd Generation (3G) wireless packet data communication system, such as, for example, HSDPA, HSUPA or HRPD, uses technologies such as Adaptive Modulation and Coding (AMC) and Channel-Sensitive Scheduling (CSS) to improve transmission efficiency. A transmitter can adjust a data transmission amount according to a channel state using AMC. Specifically, when the channel state is ‘bad’, the transmitter reduces the data transmission amount to match the reception error probability to a desired level, and when the channel state is ‘good’, the transmitter increases the data transmission amount to transmit a larger volume of information efficiently while matching the reception error probability to the desired level. Since the transmitter selectively services a user having a superior channel state among several users, the transmitter can increase the system capacity using the CSS resource management method, as compared with a transmitter that allocates a channel to one user and services the user with the allocated channel. Such a capacity increase is commonly referred to as a multi-user diversity gain. The AMC method and the CSS method receive partial channel state information that is fed back from a receiver, and apply an appropriate modulation and coding technique at the most efficient time determined depending on the received partial channel state information.
When using AMC along with a Multiple Input Multiple Output (MIMO) transmission scheme, it may be necessary to consider a number of spatial layers and ranks for transmitting signals. In this case, the transmitter determines the optimal data rate in consideration of the number of layers for use in MIMO transmission.
Recently, research has been conducted to replace Code Division Multiple Access (CDMA) used in legacy 2nd and 3rd mobile communication systems with Orthogonal Frequency Division Multiple Access (OFDMA) for a next generation mobile communication system. The 3GPP and 3GPP2 are currently standardizing an OFDMA-based evolved system. OFDMA is expected to provide superior system throughput as compared to CDMA. One of the main factors that allows OFDMA to increase system throughput is the frequency domain scheduling capability. As CSS increases the system capacity using the time-varying channel characteristic, OFDM can be used to obtain more capacity gain using the frequency-varying channel characteristic.
Also, research has focused on a Coordinated Multi-Point Transmission/Reception (CoMP) technique which enables a UE to receive signals from multiple base stations, such as, for example, enhanced Node Bs (eNBs).